Until that remarkable twist of fate became clear years later, when that infant blossomed into Lamine Yamal.
Now those images of the long-haired Messi, his hands covered in soap suds as if anointing Yamal as soccer's Next Big Thing, have become the most talked about - and gawked about - in the runup to Sunday's World Cup final, when Messi's Argentina will play Yamal's Spain for the biggest trophy in the sport.
"I have never been a believer or thought that anything was destined to occur, but I am beginning to have my doubts. This is beyond all reasonable explanations," Monfort told The Associated Press from his home in Barcelona on Friday.
Monfort, who works as a freelance photojournalist for the AP, took the photos in 2007 as part of a charity calendar produced by local newspaper Sport and UNICEF.
Luck dictated that Yamal's mother, who appears in the calendar photo, won a raffle of families in the city of Mataró, near Barcelona, who wanted to participate. Soccer destiny then deemed that her baby boy, who would become a star for Barcelona some 15 years later, was paired up with the Argentine who would become one of the greatest of all time.
A tearful Messi left Barcelona in 2021 when the club was in financial trouble. Yamal erupted at the club two years later. The journey is now complete, from bathtub to World Cup final, where the 19-year-old Yamal will face a Messi who is 20 years his senior.
"He is one of the best players in the world right now, so I wish him the best. He's only 19 years old and he has all of his future ahead," Messi said in Spanish on Friday.
"That picture, it was crazy. Him as a baby, and now we are facing each other. What a crazy picture. I just wish him the best of luck."
The famous photo taken in Barcelona's Nou Camp dressing room was forgotten until ...
Monfort had no recollection of the photos until Yamal's father posted one on social media during the 2024 European Championship, when a teenage Yamal was enjoying his international breakout and led Spain to the title.
The photo went viral then. But now, with the World Cup final looming, Monfort said interest in his photos has skyrocketed.
"This has exploded all over the world, and the fact that the final is in the US has given it the extra push," Monfort said. "And now this has culminated with the final between Messi and Yamal. It is better than any film script."
Monfort said he has been bombarded by queries for the photos by professional media outlets, while also seeing his images reproduced countless times on social media and the internet without any credit or compensation.
Yamal's Spain teammate Mikel Merino had the same reaction as most people who see the photos.
"The first time I saw it, I thought it was AI and that it wasn't even real," Merino said Friday.
"It's unbelievable that two of the best players to have played the game - and hopefully Lamine, in the future, will be one of those - share a picture like that.
"Hopefully we're going to see a very bright final with those two protagonists at their best, playing and giving all the fans a great spectacle."
Barcelona fans are torn by love of both Messi and Yamal.
Like many Barcelona fans, Monfort's loyalty is split. It is common to see children wearing both Yamal's Barcelona and Spain shirts, as well as any Messi shirt, whether from his Barcelona years or Argentina or his current club, Inter Miami, on the city's streets.
Monfort, 58, is considering travelling to see the final in New Jersey, but whether he watches it in person or at home, he said he will have trouble cheering for one team or the other.
"My heart is split. I don't know if I want Messi or Yamal to win," said Monfort, a lifelong Barcelona supporter.
"I have an everlasting love for the best player of all time (Messi)," he said, but "Yamal has broken the mould here" and represents a new, diverse Spain, thanks to his parents from Morocco and Equatorial Guinea.
"Maybe they can both win. I wouldn't rule it out after everything we have seen."
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